In the prior art, many processes have been proposed or used for sterilization such as, for example, wet or dry heat, chemicals, ionizing radiation, electron beams, microwaves, arc discharges, lasers, and plasmas. Heat, penetrating radiation, or chemicals, have been preferred for sterilizing articles of irregular shape which may contain a variety of narrow apertures, holes, or tubes, because of their ability to effectuate sterilization within these types of features.
While wet or dry heat at sufficiently high temperatures is effective for sterilization, its use is restricted to those articles which can remain undamaged by the temperature required (typically 120.degree.-170.degree. C. for 15-60 minutes). Thus, large classes of temperature or moisture sensitive articles cannot be sterilized in this manner.
A particular problem with the use of chemicals, e.g. ethylene oxide, is the length of time required to process a single batch, about 24 hours. In addition, chemical sterilization agents suffer from problems of toxicity and limited shelf life.
Ionizing radiation must be of sufficient high energy to penetrate the articles in order to be effective in sterilization of the complex shapes being considered here. This necessitates the use of x-rays and/or gamma rays, both of which require large and expensive apparatus, and are generally hazardous.
Using a plasma to sterilize articles which contain long, narrow apertures (e.g. blood capillary passages) is disclosed in U.S. Pat. Nos. 3,851,436 and 3,948,601. However, the system and method described therein function by passing a continuous flow of a separately generated plasma through the capillary passages of the articles being sterilized. Such an arrangement is not useful for articles whose openings or apertures are not continuous or which cannot be conveniently arranged to be in series with the gas flow. Additionally, the requirement for a separate chamber for plasma generation is less convenient than an arrangement in which plasma generation and sterilization take place within the same chamber.
Thus, a need exists for an improved method and apparatus which will permit the sterilization of articles of complex shape, and articles containing long, narrow holes, apertures or cavities, particularly where these articles are temperature sensitive. Accordingly, it is an object of this invention to provide an improved apparatus and method for sterilization of objects and articles of irregular shape.
It is an additional objective to provide an improved apparatus and method for sterilizing articles having long, narrow apertures, holes, or cavities therein.
It is a further object of this invention to provide an improved method and apparatus for the sterilization of thermally fragile articles at low temperature.
It is a further object of this invention to provide a plasma sterilization method and apparatus wherein active species of the plasma are carried into the pores, openings, and apertures of the complex shaped article being sterilized.